1. Field of the Invention
The present invention relates to winches and more particularly to winches having a brake-clutch assembly which frictionally engages the inside of the winch drum. A typical use of the present winch is to mount it on the front or rear bumper of a motor vehicle where it may be utilized in any of the various known modes. The winch may also be used in various industrial applications.
2. Description of the Prior Art
Prior art winches typically include a cable winding drum which is rotatably driven by a reversible electric or hydraulic motor or other type of power device. A speed reducing drive train is interposed between the hydraulic or electrical motor and the drum in order to provide torque amplification and also to reduce the typically relatively high speed of the motor. A brake assembly is commonly operably interconnected to the drive train to prevent unwinding of the drum when the motor is stopped and a load is attached to the cable. When the winch is being operated to pay out the cable to lower a load, the brake prevents the drum from overrunning the motor, thus acting as a governor to limit the cable payout speed. An inherent characteristic of such winches is the generation of heat when the cable is loaded and the brake is applied to limit the rotational speed of the drum when lowering the load.
In one type of prior art winch, the brake is composed of a plurality of thin, alternating friction discs and steel discs with either the friction or steel discs splined to a portion of the winch which is stationary relative to the drum while the other discs are splined either directly or indirectly to the drum. Means are provided to squeeze the friction discs and steel discs together either to stop or to control the rotational speed of the drum. When the brake is in constant use, large amounts of heat are produced in the discs as they rub against each other. If the discs are heated to a high temperature, the friction material on the friction discs may become glazed and/or the discs may warp, thereby reducing the effectiveness of the brake. As a result, increased squeezing pressures must then be applied to the brake discs to control the speed of or to stop the drum, thereby generating even larger amounts of heat causing further damage to the brake discs. Examples of prior art winches using this type of brake are disclosed by Henneman U.S. Pat. Nos. 3,107,899; Magnuson 3,319,492; Eskridge 3,627,087; Christison et al 4,118,013; Henneman et al 4,185,520; and, Hrescak 4,227,680.
In another type of winch, a brake assembly is composed of a central disc or ring which is squeezed between a pair of circular or annular brake pads disposed on opposite sides of the central disc. Typically, either the disc or one of the pads is anti-rotationally connected to the housing or some other stationary portion of the winch while the opposite member is directly or indirectly coupled to the drum. Means are provided for pressing the brake pads against the center disc. Examples of this type of winch are disclosed by Armington U.S. Pat. Nos. 2,891,767 and Kuzarov 4,004,780. In Kuzarov U.S. Pat. No. 4,004,780, a plurality of friction buttons extend through axial holes formed in a central disc to engage against the brake pads. Although the central disc of the brake assemblies disclosed in these two patents are thicker than the friction discs of the brake assemblies of the previously described patents, the discs still do not have enough mass to dissipate the heat generated during constant braking of the drum at a rate fast enough to prevent a substantial rise in temperature in the brake assembly, leading to reduced effectiveness of the brake assembly.
In another type of winch, a frustoconically-shaped recess is formed in one flange of a winch drum to receive a correspondingly-shaped disc which is anti-rotationally mounted on a base plate. A linkage system is provided to axially shift the disc into engagement with the drum flange to control the rate at which cable is payed out from the drum. An example of this type of winch is disclosed in Fouse U.S. Pat. No. 1,285,663. A limitation of this type of winch is that the brake disc is not capable of modulating the rotational speed of the drum during powered pay out of the cable.
Accordingly, it is one object of the present invention to provide a winch having a brake-clutch assembly which frictionally bears against the inside diameter of the winch drum thereby utilizing a substantial mass and surface area of not only the winch drum, but also the steel cable wound around the drum to rapidly dissipate the heat generated during braking, especially when operating the winch under power to pay out or lower a substantial load. It is also an object of the present invention to provide a winch having sufficient gear reduction to provide the necessary torque amplification to minimize the required horsepower of the motor while also minimizing the overall size of the winch.
The prior art also includes the winch shown in co-pending Telford Serial No. 406,778 filed Aug. 10, 1982 entitled "Winch" now U.S. Pat. No. 4,461,460. That winch construction is generally satisfactory, however two problems have been noted during its production. The first problem is that nicks or burrs on the outside edge of the clutching double ring gear 158 tend to prevent ring gear 158 from sliding longitudinally as it should when actuating lever 164 is rotated. The second problem is that ring gear 158 is relatively long and thus any lubricant which may be between the spinning ring gear 158 and the stationary end housing 127 tends to act as a viscous clutch thereby causing excessive drag during free spool cable pull out.
Accordingly, it is another object of the present invention to provide a winch construction embodying a clutching ring gear which does not slide longitudinally and which is not subject to excessive viscous clutch drag from the lubricant.
A production version of the winch shown in Telford Ser. No. 406,778, now U.S. Pat. No. 4,461,460, utilizes a permanent magnet-type of electric motor the shaft of which, when the electrical current to the motor is switched off, has inherently a high resistance to rotation. If the motor is switched off while that winch is operating to reel in a load supported by the cable, the inherent high resistance to rotation of the motor shaft holds the drive cam member 72 which in turn causes the cam follower 74 to ramp up the cam surface 94 which in turn causes the brake-clutch assembly 24 to automatically frictionally lock the drum spool to hold the load by preventing reverse rotation of the drum. Thus, the actuator assembly 68 in that winch utilizes the high resistance to rotation of the switched off permanent magnet motor shaft in order to lock the drum.
Accordingly, it is another object of the present invention to provide a brake-clutch assembly for a winch which does not require the high resistance to rotation provided inherently by a permanent magnet-type of motor. Thus, it is sometimes preferred to employ a series-wound type electric motor in a winch and such motors do not possess a high resistance to rotation when the electric current is switched off. Hence, one of the advantages of the present invention is that the brake-clutch assembly provides excellent locking of the drum in a winch with a series-wound motor.